Chemically tailored block copolymers for highly reliable sub-10-nm patterns by directed self-assembly

While block copolymer (BCP) lithography is theoretically capable of printing features smaller than 10 nm, developing practical BCPs for this purpose remains challenging. Herein, we report the creation of a chemically tailored, highly reliable, and practically applicable block copolymer and sub-10-nm line patterns by directed self-assembly. Polystyrene-block-[poly(glycidyl methacrylate)-random-poly(methyl methacrylate)] (PS-b-(PGMA-r-PMMA) or PS-b-PGM), which is based on PS-b-PMMA with an appropriate amount of introduced PGMA (10–33 mol%) is quantitatively post-functionalized with thiols. The use of 2,2,2-trifluoroethanethiol leads to polymers (PS-b-PGFMs) with Flory–Huggins interaction parameters (χ) that are 3.5–4.6-times higher than that of PS-b-PMMA and well-defined higher-order structures with domain spacings of less than 20 nm. This study leads to the smallest perpendicular lamellar domain size of 12.3 nm. Furthermore, thin-film lamellar domain alignment and vertical orientation are highly reliably and reproducibly obtained by directed self-assembly to yield line patterns that correspond to a 7.6 nm half-pitch size.

In conclusion, the manuscript by Maekawa et al. is a very promising and well-executed study on the directed self-assembly of block copolymers yielding sub-10 nm patterns.To strengthen the scientific impact and relevance of the paper, it is crucial to include a more comprehensive comparative analysis of their results with other recent findings in the literature.This addition will increase the scientific rigor of the manuscript and aid in its evaluation for publication in Nature Communications.
Reviewer #2 (Remarks to the Author): This article claims the smallest perpendicular lamellae assembled from block polymers which had a 12.3 nm domain size.As apparent in review articles elsewhere (10.1021/acsmacrolett.5b00472)and the introduction here, this is a very crowded field with widespread similar claims where this article appears to slightly advance the state of the art.
It must be pointed out that while this polymer-lithography field is scientifically interesting, it does not appear to be technologically relevant.Since 2022 production lithography at TSMC has reached 3 nm feature sizes and did so with far lower defect densities and complete design flexibility.This disconnect from rational utility significantly tempers the enthusiasm and possible impact of this work.
The article is not particularly written for a general nature-style audience, and reads rather more like a Macromolecules article.It is also not written as a communication as it feels exceedingly long.While I do not feel this article is a good fit for Nature Comm, I can offer suggestions for how to improve it for future review elsewhere: 1) The parabolic trajectory of X with mol% PGMA (Fig 4b) should be explained in terms of theory/models.Seems like a missed opportunity to reflect more deeply upon the data.
2) The SAXS experiments to measure X were not sufficiently described.How did the authors measure the instrumental broadening factor (beam smearing)?How did the authors account for this instrumental affect when calculating X values?
3) The chemical sketches (Fig 2 ) were too small to be read easily.Changing the layout would allow more room for the figure to be readable.

Reviewer #3 (Remarks to the Author):
This manuscript reported route to increase the χeff by introducing 2,2,2-trifluoroethyl groups into the PMMA segments in PS-b-PMMA.Two kinds of PS-b-PMMA derivatives with higher χ values are obtained, which maintain the surface and interfacial properties of PS-b-PMMA.The work is important and publishable, but the following issues would be suggested to address.
1.In introduction, the first and second paragraphs are repetitive, and need to be trimmed.Besides, the presentation of the background focuses entirely on the method of increasing the χ value, and needs to be expanded.
2. Why does PS-b-PGM10-22 exhibit a disordered structure?Try to state the reason if there is one.
3. The positioning of numbers and text in the Tables needs to be adjusted, which are not aesthetically pleasing enough.
4. Some ticker labels should be removed in some Figures such as Fig

Point to Point Response to the Reviewers Manuscript ID; NCOMMS-23-40950A
We sincerely appreciate the editor and reviewers' valuable and insightful comments on our manuscript.We have revised and improved our manuscript as suggested.In the following, we provide a point-to-point response to every question raised.We have highlighted portions of the manuscript that have been updated in response to the reviewers' comments.
Reviewer #1 (Remarks to the Author): In their manuscript, Maekawa and colleagues present a significant advance in the directed self-assembly of block copolymer lamellae on chemically patterned substrates, resulting in line patterns with pitches as small as 12 nm.The key innovation lies in their novel synthetic approach, which involves post-functionalizing polystyrene-block-[poly(glycidyl methacrylate)-random-poly(methyl methacrylate)] (PS-b-(PGMA-r-PMMA) or PS-b-PGM) block copolymers with thiols, specifically 2,2,2-trifluoroethanethiol.This method increases the Flory-Huggins interaction parameters (χ) by 3.5-4.6times compared to conventional PS-b-PMMA, which is a critical factor in achieving sub-10 nm period sizes through block copolymer self-assembly.The study relies on standard characterization techniques such as small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) to confirm the lamellar structures and spacings.In addition, the authors use disordered-SAXS profile fitting based on the established Leibler mean-field theory to calculate the Flory-Huggins interaction parameters.
The authors use well-established protocols to fabricate patterned substrates, specifically sparse line patterns with chemical contrast.These substrates were prepared by modifying silicon wafers with a silicon nitride (SiN) layer and using PS chemical guides for directed self-assembly.Adding PS-r-PMMA-r-PHEMA random copolymers to these substrates enables the directed self-assembly of a series of PS-b-PGFM block copolymers, ultimately forming 12 nm line patterns.
Overall, this work is compelling and represents a notable contribution to the directed self-assembly of block copolymers for next-generation lithography.The synthesis of block copolymers with enhanced interaction parameters is a critical step towards achieving sub-10 nm feature sizes through self-assembly.The data presented in this manuscript are of high quality.The study covers a comprehensive spectrum, including structural characterization, determination of interaction parameters, and successful fabrication of small pitch line patterns through directed selfassembly. .